Selective angiography has confirmed the importance of preserving the external carotid system in the treatment of vascular tumors of the head. Temporary occlusion of the external carotid artery provides satisfactory control of bleeding during surgical procedures, without affecting the future blood supply. On the other hand, permanent ligation of the external carotid artery usually results in the development of a rich collateral circulation from the internal carotid and vertebral systems, and complicates the control of bleeding during subsequent operations.
von Leden H, Wilson GH, Turnbull FM. Control of Bleeding During Surgery on Vascular Tumors of the Head. JAMA. 1968;205(8):563-566. doi:10.1001/jama.1968.03140340033007